The aim of the proposed research is to elucidate some of the biochemical events preceding the development of functional adrenergic neurons in chick sympathetic ganglia, focussing upon two points: their relation to a) the establishment of synaptic connections in the ganglion and b) the initiation of functional activity at hatching. The study will essentially involve measuring the activity of enzymes related to the synthesis and inactivation of neurotransmitters throughout development from the earliest stages to the prenatal ones until 60 days after hatching (a.h.). Measurements will be taken a) under normal conditions of development, b) after administration of different pharmacological agents which are known to modify the levels of amines either in the cell body or in the peripheral synapse, and to lead to permanent changes in levels of biosynthetic enzymes, and c) after preganglionic denervation in the first hours after hatching. This project is made possible through the recent development of sensitive micromethods for assaying enzyme activity in microgram samples of nervous tissue.